Use bolder display sans font

For advertisement features

## Before

![screen shot 2014-08-18 at 12 14 53](https://cloud.githubusercontent.com/assets/74132/3950647/02cc23ce-26c9-11e4-9f8e-c6f0ac72ff95.png)

## After

![screen shot 2014-08-18 at 12 14 56](https://cloud.githubusercontent.com/assets/74132/3950649/077de51a-26c9-11e4-9a77-c6a0548a69b9.png)

cc: @paulrobertlloyd